The immediate goal of this project continues to be the establishment of high titered scrapie infected tissue culture cell lines. Scrapie is a naturally occurring spongiform encephalopathy of sheep and goats which causes clinical and pathological changes similar to those of Creutzfeldt-Jakob and Kuru diseases of man. Scrapie grows to high titer in mouse lymphoid tissue and brain but has never been passaged at high titer in any in vitro system. Adaptation of the agent to cell culture will permit detailed characterization of the agent(s) and provide a system for better definition of the pathogenesis of these diseases. We have utilized two approaches designed to provide infected in vitro cell lines. In one approach, scrapie infected mice are injected with one of several splenotropic tumor cell lines. Once tumors are established in vivo, they are explanted, maintained in vitro and assayed for the presence of scrapie agent. The second approach utilized hybridoma technology. Spleen cells from scrapie infected mice are fused with a myeloma cell line. If a scrapie infected cell was a partner in the fusion, persistently infected lines might result. Preliminary results suggest that the hybridoma approach was unsuccessful and results of the tumor experiments are not yet available. Other experiments designed to identify scrapie target cells in mouse spleen indicate that only one in one thousand or more cells is infected. It is, therefore, likely that if a particular cell is preferentially infected, it is a subpopulation of one of the major phenotypes (T or B) now known and that currently available cell separation techniques are not likely to isolate them in sufficiently pure form to allow their characterization. Attempts to adapt the agent to a tumor system will therefore be emphasized.